[PATCH v2 net-next] skmsg: convert struct sk_msg_sg::copy to a bitmap

[PATCH v2 net-next] skmsg: convert struct sk_msg_sg::copy to a bitmap

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

We have plans for increasing MAX_SKB_FRAGS, but sk_msg_sg::copy
is currently an unsigned long, limiting MAX_SKB_FRAGS to 30 on 32bit arches.

Convert it to a bitmap, as Jakub suggested.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
v2: Sent as a stand alone patch.

 include/linux/skmsg.h | 11 +++++------
 net/core/filter.c     |  4 ++--
 2 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
index 18a717fe62eb049758bc1502da97365cf7587ffd..1ff68a88c58de0dc30a50fd030b49ea55a6c2cb9 100644
--- a/include/linux/skmsg.h
+++ b/include/linux/skmsg.h
@@ -29,7 +29,7 @@ struct sk_msg_sg {
 	u32				end;
 	u32				size;
 	u32				copybreak;
-	unsigned long			copy;
+	DECLARE_BITMAP(copy, MAX_MSG_FRAGS + 2);
 	/* The extra two elements:
 	 * 1) used for chaining the front and sections when the list becomes
 	 *    partitioned (e.g. end < start). The crypto APIs require the
@@ -38,7 +38,6 @@ struct sk_msg_sg {
 	 */
 	struct scatterlist		data[MAX_MSG_FRAGS + 2];
 };
-static_assert(BITS_PER_LONG >= NR_MSG_FRAG_IDS);
 
 /* UAPI in filter.c depends on struct sk_msg_sg being first element. */
 struct sk_msg {
@@ -234,7 +233,7 @@ static inline void sk_msg_compute_data_pointers(struct sk_msg *msg)
 {
 	struct scatterlist *sge = sk_msg_elem(msg, msg->sg.start);
 
-	if (test_bit(msg->sg.start, &msg->sg.copy)) {
+	if (test_bit(msg->sg.start, msg->sg.copy)) {
 		msg->data = NULL;
 		msg->data_end = NULL;
 	} else {
@@ -253,7 +252,7 @@ static inline void sk_msg_page_add(struct sk_msg *msg, struct page *page,
 	sg_set_page(sge, page, len, offset);
 	sg_unmark_end(sge);
 
-	__set_bit(msg->sg.end, &msg->sg.copy);
+	__set_bit(msg->sg.end, msg->sg.copy);
 	msg->sg.size += len;
 	sk_msg_iter_next(msg, end);
 }
@@ -262,9 +261,9 @@ static inline void sk_msg_sg_copy(struct sk_msg *msg, u32 i, bool copy_state)
 {
 	do {
 		if (copy_state)
-			__set_bit(i, &msg->sg.copy);
+			__set_bit(i, msg->sg.copy);
 		else
-			__clear_bit(i, &msg->sg.copy);
+			__clear_bit(i, msg->sg.copy);
 		sk_msg_iter_var_next(i);
 		if (i == msg->sg.end)
 			break;
diff --git a/net/core/filter.c b/net/core/filter.c
index 9615ae1ab530a9735e3d862b1ddf12b1b1f55060..f497ca7a16d223855004876e3a868d5de8cea879 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2603,7 +2603,7 @@ BPF_CALL_4(bpf_msg_pull_data, struct sk_msg *, msg, u32, start,
 	 * account for the headroom.
 	 */
 	bytes_sg_total = start - offset + bytes;
-	if (!test_bit(i, &msg->sg.copy) && bytes_sg_total <= len)
+	if (!test_bit(i, msg->sg.copy) && bytes_sg_total <= len)
 		goto out;
 
 	/* At this point we need to linearize multiple scatterlist
@@ -2809,7 +2809,7 @@ BPF_CALL_4(bpf_msg_push_data, struct sk_msg *, msg, u32, start,
 	/* Place newly allocated data buffer */
 	sk_mem_charge(msg->sk, len);
 	msg->sg.size += len;
-	__clear_bit(new, &msg->sg.copy);
+	__clear_bit(new, msg->sg.copy);
 	sg_set_page(&msg->sg.data[new], page, len + copy, 0);
 	if (rsge.length) {
 		get_page(sg_page(&rsge));
-- 
2.35.0.263.gb82422642f-goog

Re: [PATCH v2 net-next] skmsg: convert struct sk_msg_sg::copy to a bitmap

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (master)
by David S. Miller <davem@davemloft.net>:

On Fri,  4 Feb 2022 20:56:14 -0800 you wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> We have plans for increasing MAX_SKB_FRAGS, but sk_msg_sg::copy
> is currently an unsigned long, limiting MAX_SKB_FRAGS to 30 on 32bit arches.
> 
> Convert it to a bitmap, as Jakub suggested.
> 
> [...]

Here is the summary with links:
  - [v2,net-next] skmsg: convert struct sk_msg_sg::copy to a bitmap
    https://git.kernel.org/netdev/net-next/c/5a8fb33e5305

You are awesome, thank you!
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